Electric converter



July 21, 1931.

G. B. CROUSE ELECTRIC CONVERTER Filed Jan. 6, 1927 i atented July 21, 1931 UNITED STATES GEORGE B. GROUSE, OF WOODCLIFF,

NEW YORK PATENT orricn NEW JERSEY, ASSIGNOR, BY MESNE nssre'nirnnrsl 'ro NATIONAL CARBON COMPANY, Inc,

OF NEW YORK, N, 1., A CORPORATION OF ELECTRIC CONVERTER Application filed January 6, 1927. Serial No. 159,454.

This invention relates to electric converters and more particularly to apparatus adapted to convert current derived from the ordinary house lighting circuits into currentv suit- 6 able for the operation of audion amplifier circuits. 7

The presence of alternating components in the current supplied from direct current lighting circuits or obtained by rectification 19 from alternating current lighting circuits renating components,

sults in disturbances when such currents are supplied to the circuits of the usual audion amplifiers or radio receivers. Commutator ripples may be eliminated from a direct current supply circuit by means of filters, and smooth direct current may be obtained from an alternating current supply by means of rectifier and filter combinations. The problem of utilizing a house lighting circuit as a source of supply for energizing audion circuits has not been solved, however, by the construction of apparatus capable of. converting current from the power line into smooth direct current sinceother'difliculties arise when such apparatus is employed with an amplifier such as a radio receiver.

Proposed devices capable of delivering smooth direct current to a radio receiver have failed to operate satisfactory for many reasons, and principally for one or-more of the following reasons: variations in lighting circuit voltage caused troublesome variations in the voltage supplied to the receiver; variations in the load caused wide variations in the 5 output voltage of the converter-filter apparatus; the character of. the impedances introduced intothe plate circuits of the audions by the filter mesh resulted in interstage coupling and consequent distortion or instability in the receiver; no satisfactory means was provided for obtaining a bias voltage for the grids of audio amplifiers; and the condensers and the insulation of other elements of the filter mesh were liable to damage from surges set up when the converter-filter circuits were opened and closed.

An object of the invention is to provide apparatus operable from a source of alternating current, or of current containing alterwhich apparatus will not be affected in its operation by the nature of the load. to-which it supplies a smooth direct current and which is of such construction that it will not provide undesired couplings between portions of the load circuit which it supplies. A further object is to provide apparatus of the type stated which, when operated with radio receivers, will be free from the stated defects in prior devices. An ob ect is to provide apparatus of the type stated and from which a grid bias potential may be derived without causing audio fre quency distortion in a radio receiver. More specifically an object is to provide'apparatus of the type stated in which a source of smooth direct current forms, in effect, a section of the filter networlrof the apparatus.

These and other objects of the invention Will be apparent from, the followingdescription when taken with the accompanying drawing which comprises a circuit diagram illustrating one embodiment of the invention as associated with a typical radio receiver.

The apparatus as shown in the figure is designed for use with a source of alternating current and includes a transformer having a primary winding 1 which may be perinanently connected to an alternating current lighting circuit bythe terminals 2, 3. The transformer, which may be of the usual design, has an iron core 4:, a secondary winding 5, andan additional secondary winding 6 for energizing the filament 7 of the rectifier 8. The rectifier may be of any desired construction'but is illustrated as of the hot cathode high vacuum type, the plate 9 of the rectifier serving, with one side of the secondary winding 5, as the terminalsof the rectified current-line. The other terminal of the secondary 5 is connected'to the midpoint of the filament winding 6 in the usual manner, and preferably a small capacity-1O is shunted across the secondary winding 5. The filter mesh is of conventional type and includes a series inductance l1 wound on .an iron core 12 and arranged in the positive line between the two shunt capacities 13, 14.

The construction, so far as above described, is typical of known systems for obtaining rectified and filtered current from an alter nating current source. The respective junctions 15, 16 of the condenser 14 With the positive and negative leads of the filter mesh serve as terminals from Which direct current may be obtained. The voltage of the direct current and the degree of suppression of alternating components are dependent upon the design of the transformer, rectifier and filter elements. Apparatus of this type may be readily constructed to deliver direct current of such voltage .and such freedom from alternating components that the device may be used to energize the plate circuit of a single stage of audio frequency amplification. The usual practice for obtaining voltages of an order less than that existing between terminals l5, 16 has been to shunt a tapped resistance or potentiometer across the terminals.

In accordance with this invention, an additional filter section is provided by elements which are serially connected to form a path in shunt across the output terminals of the known filter mesh.

As shown in the circuit diagram, the series elements of the added filter section comprise an impedance 17, a battery 18, and. a resistance 19. The manner in which this filter section modifies the operation of a customary co1'1verter-filte'r system or battery eliminator may be best understood by first considering the plate current requirements of a typical radio receiver.

The typical radio receiver which is shown in the diagram includes one stage of tuned radio frequency amplification, an audi'o'n detector, and two stages of audio frequency amplification. The input circuit-0t the audion R of the radio frequency 'sta'ge comprises a transformer having a primary 20 connected in the antenna circuit and a secondary 21 which is shunted by the tuning condenser 22. The radio frequency stage feeds into detector audion D through the radio frequency transformer 23, and preferably a small condenser 2-1 connects the lower terminal of the transformer primary to the filament to complete the radio frequency circuit indepen dent' of the plate power supply. Detector tube D feeds into the first audio amplifier A by means of an iron core audio frequency transformer 25, a bypass for radio frequency currents being provided by the condenser 26. The input circuit of the last audio stage is provided by the secondary of the audio frequency transformer 27, the pri mary of the transformer being included in the plate circuit of the audion A. The audion PT of the last audio stage is of the power tube type and the output circuit of the audion includes a loud speaker 28.

The filaments of th'eseve'ral tubes are supplied with current from a battery 29 and suitable resistances or ballast devices, not shown, may be included in the filament circuits for regulating the current supply to the several filaments. A feature of the invention comprises a simultaneous control of the filament and plate circuits. This is effected by including a relay or magnetic switch 30 in the filament circuit of the rectifier tube 8 and connecting the Winding 31 of the switch as a series element of the filament supply circuit of the receiver. A hand operated switch 32 controls the supply of current to the filament and, through the relay switch, simultaneously controls the operation of the plate current supply system.

For purposes of illustration, it may be as the usual types of audions are sumcd tl emp yed in the radio receiver. It is-customobt. the desired grid bias for radio y amplifiers-1 and audion detectors by the grid ii'eturnsof such stages to mate filament terminal of the par- The plate voltage of a radio may be 90 volts While the rector stage is usually 4:5 no stages employing voltage of 90 volts and its is the usual practice. stage employing a power tubc, erates satisfactorily with ate when a negative bias r of i volts applied to the grid. ug now to the comerter-filter sysbatterylS Which forms an elei. cnt 'ly Wiil preferably be of such ilate circuits of all tubes e:-:- o PT may be complcteu Que side of. the audr'rzn i I connected to the point the battery 18 a d thus forms a ."=turn for all of the plate circuits. hat the several audions are of the --)Q(3i.'ita?ti under vo ge conditions as te above, the battery 1c will have ma iive potential, vith respect to point 3 oreer of 90 volts. The lower sides 7 mary windings of radio frequency transioriucr F23 and audio frequency transformer i)? are connected to each other and to 00 volt terminal of the battery 18. The

of the first audio frequency trans- 25 is connected to an intermedi of the battery to apply 4- e of detector audion I The grid in amplifier A is obtained by connecti grid return of that tube to the ncga 'ininal, l of the battery 18, Wh ch termuial so related to the point B that bias voltage of 4 impressed upon the grid of audion it The plate pct 11 for power tube PT is obtained directly fro. i the positive line of the converter-filter system and the 'rid return for that tube is connected di. :v to the to the pl bias for quirements of the radio receiver. )n the the point drawing, the legends +180 and as applied to the positive and negative lines, respectively, indicate voltages with respect to B which may be used with the present commercial types of power tubes. It is to be understood that the invention is in no way limited to the particular voltages which have been recited as illustrative of the requirements of a common type of radio set. The invention of course contemplates that the converter will be designed to deliver voltages of the orders determined by the needs of the radio set or other equipment with which the apparatus is to be employed.

In any particular installation, the resistances of the impedance elements in series with the direct current source 18 are preferably so chosen that under the allowable variations of line voltage and/or of the value of the load, the direct current source 18 either floats on the line (neither taking up nor giving out energy) or charges or-discharges by a small amount. The source of direct current is characterized by a low internal resistance, high capacity and a back electr-omotive force of considerable magnitude. Either dry or wet cells may be employed as the source of direct current, and 'n practice the ordinary dry batteries such as are now used as a plate current supply have been found to be well adapted for use as the direct current source 18.

Several important advantages are obtained when the direct current supply apparatus is constructed in accordance with the present invention.

Intermediate points in the shunt impedance path which is provided across the terminals 15, 16 by the series elements 17, 18 and 19 serve as terminals for obtaining the intermediate voltages customarily required in radio receivers. The shunt path also functions as an additional section of the filter mesh. It is well known that a degree of filtering satisfactory for the operation of the last stage of an amplifier will not ordinarily be sufiicient for the operation of the earlier stages in a cascaded chain. In accordance with this invention only the last stage is energized directly from the output terminals 15, 16 of the filter mesh. The elements of the filter may be designed with reference to the requirements of the output stage as an additional filtering of current for supply to the earlier stages is effected by the auxiliary mesh to which those stages are connected. The impedance 17 will ordinarily be a pure resist ance but may comprise a resistance and an inductive impedance in series when extreme filtering is required. The direct current source 18 cooperates with the impedance 17 to form the filter section and, from the viewpoint of filter operation, is the equivalent of a very large capacity. The resistance 19 also contributes to the filtering of the intermediate potentials and at the same time provides the necessary potential drop'to bias the grid of the last audio stage.

The action of the direct current source is not, however, limited to its operation as a capacitive element of a filter mesh. Due to its back electromotive force, coupled with a reasonably low internal resistance, the battery functions as a voltage stabilizer or regulator to prevent fluctuations of the voltage applied to input terminals 2, 3 from afiecting any but the last stage of the receiver. Its low resistance and high capacity provide a short circuit for alternating current components set up in the last amplifier plate circuit and thus prevent such components from affecting the operation of other stages of the amplifier.

-Although the presence of the battery 18 does not eliminate all fluctuations in potential between the points 15, 16 of the filter mesh, the effect of such voltage variations in the plate circuit of the last stage is offset by the fact that simultaneous variations take place across the resistance 19 and are thus applied in opposite phase to the grid of audion. PT. In this way the-grid bias is varied in exact relationship to the plate potention applied to the tube so that, within the limits of normal variations in power line voltage, the quality of the reproduction is not changed.

The element 18, due to its low internal resistance, has the additional function of acting as an electrical cushion to prevent abnormal voltages from being set up across the condensers 13, let of the filter mesh and bypass condensers 24, 26 of the radio set.

When the constants of the auxiliary filter mesh are so chosen that the battery is floating or substantially floating on the line, theeffective life of a dry battery will be materially extended. In actual practice a dry battery in this position normally maintains itself in a condition of low internal resistance and high capacity. I conceive that the liberation of gases within the battery will cause a rise in resistance but that when the resistance reaches a certain value, the converter feeds energy into the battery and the gases are re combined thus lowering the resistance and raising the capacity. 7

It is to be noted that the relay switch 30, 31 prevents the converter from feeding energy into the battery under conditions of no load. It is to be understood that the specific constructions of the converter, filter and radio set in which the invention is incorporated or with which the invention may be associated are subject to wide variation. The character and the constants of the auxiliary impedance mesh may be adapted to meet particular requirements without departing from the spirit of the invention as set forth in the following claims.

source having terminals across I claim:

1. In apparatus for energizing the plate circuits of a plurality of audions from a source of direct current containing alternating components, a filter mesh comprising series and parallel impedance elements interposed beween the said source and said plate circuits of audions, and an auxiliary source of smooth direct current potential connected across that portion of said mesh across which certain only of said plate circuits are connected.

2. In apparatus for energizing the plate circuits of a plurality of audions, a source of alternating current, a rectifier, a filter, and a source of pure direct current connected across the output of said filter, said direct current source having a voltage adequate for the supply of the plate circuits of certain only of said audions.

3. In apparatus for delivering space current to a plurality of audions whose voltage requirements are of different orders of magnitude, a source of rectified current, a filter mesh energized by said source and having output terminals at which the residual alternating components are suppressed to such degree that the space current for the audions of maximum voltage requirement may be obtained therefrom, and an auxiliary mesh connected across said filter output terminals and comprising, in series, an impedance connected to the positive terminal and a battery source of direct current, said battery which may be connected the plate circuits of audions Whose voltage requirements are less than the maximum requirement.

4. Apparatus for supplying filtered direct current to the plate circuits of an audion amplifier of the type having stages whose voltage requirements are of different orders of magnitude, said apparatus comprising means energized from a light circuit and having output terminals delivering direct current of such voltage and sufiiciently free from. alternating components that the amplifier stage of.

maximum power requirements may be connected to said terminals, and a batter substantially floating between said terminals'and of a voltage adequate for the supply of direct current to the plate circuit of another stage of said amplifier.

Apparatus for supplying direct current to an audion amplifier, said apparatus being of the type including a filter mesh having direct current output terminals across which an audion plate circuit may be connected, and an impedance path between said terminals affording means for delivering intermediate voltages for energizing the plate circuit of another audion, characterized by the fact that a portion of said impedance path comprises a source of direct current substantially floating between said terminals and of such voltage that said other plate circuit may be connected across the same.

6. An electrical converter circuit comprising in combination, a transformer having a primary adapted to be connected to a source of alternating current and a secondary proportioned to furnish space current potential; a rectifying device associated with said transformer secondary; a filter circuit connected to said transformer secondary and rectifying device; and an auxiliary mesh connected across the output terminals of said filter circuit and comprising, in series, an impedance connected to the positive output terminal of said filter, a battery source of space current, and a second impedance connected to the negative output terminal of said filter, said battery source having terminals across which may be connected the plate circuits of audions whose voltage requirements are less than the maximum requirement.

7. An electrical converter circuit adapted to be connected between an alternating current house-lighting circuit and a radio circuit including a plurality of vacuum tubes, comprising, in combination, a transformer having a primary adaptedeto be connected to said. alternating current source and a secondary proportioned to furnish space current potential for said vacuum tube circuit, a rcctifying device associated with said transformer secondary; a filter circuit connected to said transformer secondary and rectifying device; an auxiliary mesh connected across the output terminals of said filter circuit and comprising, in series, an impedance connected to the positive output terminal of said filter, a battery source of space current and a second impedance connected to the negative output terminal of said filter; means for connecting a negative point of said space current battery to the cathodes of said vacuum tubes; means for connecting a positive terminal of said space current battery to the anode of at least one of said vacuum tubes; means for connecting the positive output terminal of said filter to the anode of another of said vacuum tubes; and means for con necting the negative output terminal of said filter to the control electrode of said lastmentioned vacuum tube.

8. An electrical converter circuit adapted to be connected between an alternating current house-lighting circuit and aradio circuit including a plurality of vacuum tubes, comprising, in combination, a transformer having a primary adapted to be connected to said alternating current source and a secondary proportioned to furnish space current potential for said vacuum tube circuit; a reetifying device associated with said transformer secondary; a filter circuit connected to said transformer secondary and rectifying device; an auxiliary mesh connected across the output terminals of said filter circuit and comprising, in series, an impedance connected to the positive output terminal of said filter, a battery source of space current, and a second impedance connected to the negative output terminal of said filter; means for connecting a negative point of said space current battery to the cathodes of said vacuum tubes; means for connecting a relatively more negative point of said battery to the control electrode of at least one of said vacuum tubes; means for connecting a relatively more positive point of said space current battery to the anode of at least one of said vacuum tubes; means for connecting the positive output terminal of said filter to the anode of another of said vacuum tubes; and means for connecting the negative output terminal of said filter to the control electrode of said last mentioned vacuum tube.

9. An electrical circuit comprising, in combination, a house-lighting source of alternating current; a radio circuit including a radio frequency amplifier tube and an audio frequency amplifier tube; an electrical converter circuit interposed between said alternating current source and said radio circuit, said converter circuit including a transformer having a primary winding adapted to be connected to said alternating current source and a secondary winding proportioned to furnish space current for said vacuum tubes, a rectifying device associated with said secondary winding, a filter circuit connected to said secondary winding and said rectifying device, and an auxiliary mesh connected across the output terminals of said filter circuit, said mesh comprising, in series, an impedance, a space current battery, and a second impedance; a connection from a negative point of said space current battery to the cathodes of said vacuum tubes; a connection from a positive point of said space current battery to the anode of said radio frequency amplifier tube; a connection from the positive output terminal of said filter to the anode of said audio frequency amplifier tube; and a connection from the negative output terminal of said filter to a control element of said audio frequency amplifier tube.

10. An electrical circuit comprising, in combination, a house-lighting source of alternating current; a radio circuit including a radio frequency amplifier tube, a detector tube, and an audio frequency amplifier tube; an electrical converter circuit interposed between said alternating current source and said radio circuit, said converter circuit including a transformer having a primary winding adapted to be connected to said alternating current source and a secondary winding proportioned to furnace space current to said vacuum tubes, a rectifying device associated with said secondary winding, a filter circuit connected to said secondary winding and said rectifying device, and an auxiliary mesh connected acrossthe output terminals of said filter circuit, said mesh comprising, in series, an impedance, a space current battery, and a second impedance; a connection from a negative point of said space current battery to the cathodes of said vacuum tubes; a connection from a positive point of said space current batter 1 to the anode of said radio frequency ampli er tube; a connection from an intermediate point of said space current battery to the anode of said detector tube; a connection from the positive output terminal of said filter to the anode of said audio frequency amplifier tube; and a connection from the negative output terminal of said filter to a control element of said audio frequency amplifier tube.

11. An electrical circuit comprising, in combination, a house-lighting source of alternating current; a radio circuit including a radio frequency amplifier tube, and a plurality of audio frequency amplifier tubes including a power tube; an electrical converter circuit interposed between said alternating current source and said radio circuit, said converter circuit including a transformer having a primary winding adapted to be connected to said alternating current source and a secondary winding proportioned to furnish space current to said vacuum tubes, a rectifying device associated with said secondary Winding, a filter circuit connected to said secondary winding and said rectifying device, and an auxiliary mesh connected across the output terminals of said filter circuit, said mesh comprising, in series, an impedance, a space current battery, and a second impedance; a connection from a negative point of said space current battery to the cathodes of said vacuum tubes; a connection from a positive point of said space current battery to the anodes of said radio frequency amplifier tube and one of said audio frequency amplifier tubes; a connection from the positive output terminal of said filter to the anode of said audio frequency power tube; and a connection from the negative output terminal of saiod filter to a control element of said power tu e.

V In testimony whereof, I afiix my signature.

' GEORGE E. GROUSE. 

